US4789657AExpiredUtilityPatentIndex 67
Process for preparing iron-based catalysts for the synthesis of ammonia and catalysts so obtained
Est. expiryJun 19, 2004(expired)· nominal 20-yr term from priority
B01J 37/00B01J 37/08B01J 23/76C01C 1/0411Y02P20/52B01J 23/745
67
PatentIndex Score
9
Cited by
6
References
10
Claims
Abstract
A process for preparing iron-based catalysts for the synthesis of ammonia by melting of magnetite along with metal oxides as promoters, subsequent cooling of the molten mass and reduction thereof to the desired size, wherein the abovesaid cooling occurs at a rate higher than 25 DEG C./min., preferably ranging from 100 DEG C. to 1600 DEG C./min., at a temperature ranging from 1700 DEG C. to 700 DEG C. The present invention relates to a process for preparing iron-based catalysts having a high activity in the ammonia synthesis, and to the catalyst so obtained.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A process for preparing an ammonia synthesis catalyst based on iron by melting magnetite or a mixture of iron oxides having the composition of magnetite, together with 1 to 10% by weight of a mixture of Al 2 O 3 , K 2 O, CaO, MgO, and SiO 2 as promoter, subsequently cooling the melt, and reducing same to the desired size, characterized in that the cooling of the melt is accomplished by quenching at a rate higher than 25° C./minute.
2. The process according to claim 1, in which the cooling by quenching of the melt is accomplished at a rate ranging from 100° C./min. to 1600° C./min. in a temperature range from 1700° C. to 700° C.
3. The process according to claim 1 or 2, in which the cooling by quenching is accomplished by pouring the melt into an iron vessel, the bottom of which consists of iron bricks having such a thickness as to secure the maximum heat dispersion.
4. The process according to claim 3, in which the thickness of the iron bricks is at least 4 cm.
5. The process according to claim 1 or 2, in which the cooling by quenching is accomplished by immersing the melt into a fluid.
6. The process according to claim 5, in which the fluid is water or air.
7. An ammonia synthesis catalyst based on iron, when prepared according to the process of claim 1 or 2.
8. An ammonia synthesis catalyst based on iron consisting essentially of magnetite together with 1 to 10% by weight of the said mixture as promoter, when prepared according to the process of claim 1 or 2, and characterized in that it has a reticular structure of the magnetite crystallites, surrounded by promoter oxide, whose sizes range from 10 to 100 μm.
9. A catalyst according to claim 8, characterized in that the sizes of the magnetite crystallites range from 10 to 40 μm.
10. An ammonia synthesis catalyst based on iron consisting essentially of magnetite together with 1 to 10% by weight of a mixture of metal oxides as defined below as promoter, and prepared by melting magnetite or a mixture of iron oxides having the composition of magnetite, together with 1 to 10% by weight of a mixture of Al 2 O 3 , K 2 O, CaO, MgO, and SiO 2 as promoter, subsequently cooling the melt, and reducing same to the desired size, characterized in that the cooling of the melt is accomplished by quenching at a rate higher than 25° C./minute, and in that the catalyst has a reticular structure of magnetite crystallites, surrounded by promoter oxide, whose sizes range from 10 to 100 μm, and further characterized in having an X-ray diffraction pattern including at least one of the two following series of lines A and B: ______________________________________
d(Å)
Intensity
______________________________________
A 8.48 VW
5.63 VW
4.57 VVW
2.94 VW
2.676 VW
2.542 VW
2.347 VVW
2.080 VW
B 5.13 VVW
2.609 W
2.477 VW
2.368 VVW
2.228 VVW
1.656 VVW
1.644 VW
1.627 VVW
1.576 VW
1.556 VVW
1.467 W
______________________________________
where "V" means very and "W" means weak.Cited by (0)
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